The invention relates to an arrangement for fastening a retaining element which consists of plastic to a metal surface, having a retaining device which interacts with a T stud, step stud or the like. The T stud has a stud shank and a stud head with an underhead with a bearing face for bearing on at least one corresponding face which is formed on the retaining device. It is possible for the stud shank to be welded to a metal surface, and the at least one corresponding face of the retaining device is configured on at least one bearing shoulder for the underhead of the stud head, which bearing shoulder encloses the stud shank at least partially.
In automotive engineering, but also generally in metal construction, it is often necessary to weld studs to workpieces, for example body surfaces, to which studs retaining elements are subsequently fastened which then serve to fix other components. During welding of studs of this type, the drawn arc stud welding method is often used, in which, at the beginning of the welding operation, the stud is first of all placed on the welding point and is subsequently lifted up by means of a lifting mechanism, first of all an auxiliary arc of low current and subsequently a main arc igniting between the stud and the workpiece. The main arc produces the material melt on the body panel and the stud base, and the stud is subsequently moved toward the workpiece and pressed onto it. The two melting zones, namely that melting zone in the base material and the further melting zone on the stud, are combined and the melting zone solidifies after the current is switched off. In this connecting operation, spraying of liquid molten material occurs, with the result that welding or melting particles can be fixed under the stud in the region of the stud underhead. Since a retaining device with a bearing shoulder, on which the underhead of the T stud comes into contact, is arranged on the retaining element, it is often the case in a contamination of this type that it is not the underhead, but rather melting or welding particles which pass between the underhead and the bearing shoulder. As a result, the fastening quality is reduced because the retaining element is not fastened in the correct position.
It is therefore an object of the invention to provide an arrangement for fastening a retaining element, in which arrangement the retaining element can be fastened correctly on the stud and post-processing of the bearing face of the underhead can be eliminated.
The object of the invention is achieved by virtue of the fact that recesses which interrupt the corresponding face are configured in the bearing shoulder.
This measure makes it possible for the welding beads to enter into the recesses in the bearing shoulder, with the result that the bearing face of the underhead can come into contact on the corresponding face. In alternative embodiments, the recesses can be of sufficiently deep configuration such that, when welding beads and the intermediate wall between the recesses come into contact, the intermediate wall can be pressed to the side. The result is that the position of the retaining element always remains positionally correct.
It is favorable here that a U-shaped passage with a circumferential side wall is formed on the retaining device, through which side wall the shank of the stud protrudes, the at least one bearing shoulder which is provided with the recesses protruding inward on the side wall, and the bearing shoulder extending continuously on the side wall around the U-shaped passage.
A multiplicity of recesses with a multiplicity of undulation peaks can be configured in the bearing shoulder. The undulation peaks in their entirety form the corresponding face. Here, the undulations are sufficiently deep that the undulation peaks can form the upper edge of a movable wall and a certain yielding movement is made possible for the edge and/or the undulation peak.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.